If a compound gauge reads 248 psig and the actual line temperature is 100°F, what is the subcooling using R-22 refrigerant?

To determine the subcooling using R-22 refrigerant based on a compound gauge reading and the actual line temperature, you will first need to convert the pressure measured in psig to a corresponding saturation temperature for R-22.

A compound gauge reading of 248 psig indicates a pressure that is measured above atmospheric pressure. To find the saturation temperature for R-22 at this pressure, you can refer to refrigerant pressure-temperature charts specific to R-22. The saturation temperature associated with 248 psig is approximately 84°F.

Subcooling is calculated by taking the saturation temperature and subtracting the current liquid refrigerant temperature from it. Here, you take the saturation temperature of 84°F and subtract the actual line temperature of 100°F.

However, to correctly calculate subcooling, you need to recognize that subcooling is only relevant when the refrigerant is a liquid; thus, if the temperature of the line is above the saturation temperature, we would expect to see a negative value. Subcooling can also be represented in terms of absolute temperature, ensuring you analyze the refrigerant behavior correctly.

In this case, if you calculate subcooling and reach a resulting value of 16°F, this signifies